The principal objective of this proposal is to determine the nature, quantitative relationships, and the mechanisms by which hormones interact in the uterus. The acute hormonal influences of myometrial contractions appear to be the direct result of effects on the intracellular concentration of cAMP. Since cAMP mediated responses typically involve the activation of protein kinase, we propose to identify and characterize the cAMP dependent-protein kinase substrates of the myometrial membranes which regulate the contraction-relaxation cycle by controlling intracellular Ca ions concentration. We propose to investigate the relationship between protein kinase, cAMP, and myometrial contraction by: 1. Purification and characterization of myometrial protein kinase. 2. Identify and characterize membrane substrates of purified myometrial protein kinase which might play a role in the control of Ca ions transport. 3. Investigate the effects of compounds which alter myometrial contractile patterns on protein kinase and its substrates. 4. Evaluate the level at which these agents operate to alter uterine motility.